<div id="app">
  <h1>{{ title }}</h1>
</div>
<script src="https://unpkg.com/vue@3"></script>
<script>
  const { createApp } = Vue

  // template => render() => vnode
  // vnode.dynamicChildren
  const app = createApp({
    data() {
      return {
        title: 'render函数'
      }
    },
  }).mount('#app')
  console.log(app.$options.render);
</script>